Notebooks, notes, and correspondence. The notebooks and notes (1874-1904) reflect the variety of Heaviside's interests; topics covered include mathematics (series expansions and calculus), mechanics (wave propagation), and electromagnetism (electromagnetic theory). Included with the notebooks are corrected galley proofs of articles on electromagnetism and theory, and the preface to the collected edition of Heaviside's Electrical Papers. Professional correspondence (1897-1922) (2 reels) is with his editors concerning publication, and with his colleagues on mathematical and electromagnetic topics. Correspondents include William E. Ayrton, Edwin H. Barton, William H. Bragg, Lord Kelvin (William Thomson), George F.C. Searle, John J. Thompson, and Silvanus P. Thompson.